Lifting jack with extendible leg structure



June 1944. T. A. HAMMOND LIFTING JACK WITH EXTENDABLE LEG STRUCTURE Filed Feb. 27, 1943 l 3 Sheets-Sheet 1 June 20, 1944- T. A. HAMMOND LIFI'ING JACK WITH EXTENDABLE LEG STRUCTURE Filed Feb. 27, 1943 3 Sheets-Sheet 2 June 20, 1944. T. A. HAMMOND 2,351,611

LIFTING JACK WITH EXTENDABLLE LEG STRUCTURE Filed Feb. 27, 1943 3 Sheets-Sheet 5 7/710M/1J/4/714/7 0N0 Patented June 20, 1944 ammo anon wrm ax'rsnnmm LEG s'raoo'roas Thomas A. Hammond, Minneapolis, Minn.

Application February 27, 1943, Serial No. 477,409

(Granted under the act of March 3, 1883. as amended Alli-i130, 1928; 370 0. G. 757) Claims.

The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to lifting Jacks, and more especially to a, tripod leg structure. the height and spread of which may be simultaneously extended in predetermined increments. It is particularly applicable to aircraft when the amount of lift is not necessarily great, but where the height from the ground of the several points to which the jack must be applied varies over a wide range.

The conventional expedient, in the design of extendible jacks, of providing a series of screws, one within the other, for covering a great range of heights is not in itself applicable to aircraft use for the reason that, as the height of the jack increases, the spread of the base must also increase in proportion to provide the required stability.

Tripods with telescoping legs are well known, but are not suitable to the purposes of this invention because no satisfactory fastening means has been proposed which will prevent one section of a telescoping leg from being forced into the other upon the application of any considerable load.

It is therefore an object of this invention to provide a Jack or light weight and small dimensions which may be extended over a wide range as between minimum and maximum heights and wherein the spread of the base on which stability depends increases in proportion to the height. A hydraulic jack has been selected to illustrate the invention, although the inventive concept is applicable to mechanically operable or other forms of jacks.

Other objects and advantages will be apparent as the invention is further described with reference to the drawings, wherein,

Fig. 1 is an elevational view of an improved a jack when substantially at minimum height and base spread.

Fig. 1a is a fragmentary view. partly in section, of the joint between a leg and its removable foot.

Fig. 2 is an elevational view showing the jack when its height and base spread have been increased by adding one leg extension to each leg and applying appropriate bracing.

Fig. 3 is an elevational view showing the Jack when its height and base spread have been further increased by adding a second leg extension to each leg and applying additional bracing members.

Fig. 4 is a fragmentary elevational view showing the Jack when its height and base spread have been further increased by adding a third leg extension to each legand applying additional bracing members.

Fig. 5 represents both a bottom view of the lower cylinder head I4 and a top view of a special bracket to which the inner ends of the leg braces are secured.

Fig. 6 is a fragmentary elevational view showing the jack when its height and base spread have been further increased by adding a fourth leg extension to each leg and applying additional bracing members.

Fig. '7 is a fragmentary view, partly in section, of the joint between one leg extension and the nex Fig. 8 is a top view of the jack when it is assembled as shown in Fig. 2.

Like numerals refer to like parts throughout the several views.

In the embodiment of the invention shown in the drawings, the lifting portion of the jack consists of a tubular cylinder Iii, an upper head I! in the form of a ring into which the cylinder is permanently secured, a lower head ll in the form of a cup into which the lower end of the cylinder is permanently secured, and a hydraulic piston I8 slidable in the cylinder.

The piston i6 is provided for the greater portion of its length with a coarse multiple thread i8 upon which a nut 20 is freely rotatable. The nut is provided for holding the piston in any extended position irrespective of the hydraulic fluid in the cylinder. The pitch of the thread i8 is sufflcient to cause the nut to settle by gravity and remain always on the upper end of the cylinder. in the positions shown, as the piston rises. At the extreme lower end of the piston, the threads are omitted for the usual hydraulic sealing means. A hose connection 22 is provided to bring the hydraulic fluid into the cylinder. A single extension screw 2! is rotatable freely in internal threads in the piston It. The amount of extension obtainable with the screw II should preferably correspond roughly to the amount the jack is raised by the addition of one extension joint in each leg. The assembly of the parts above described may collectively be referred to as the lifting unit.

Circumferentially spaced around, and preferably integral with, the upper head II are pairs of lugs 28, between which the flattened portions 28 of the legs 30 are hingedly supported by bolts 32 and wing nuts I. At the lower end, the tubular legs 30 extend snugly into the feet IO.

v The nds of the tubular legs are turned in and the corners rounded as at 38 and the shoulders in the feet against which the ends of the legs bear are correspondingly rounded as in Fig. 1a.

' Bolts 46 and wing nuts 42 hold the legs and feet ends of braces 46 are fastened to the leg and foot Joint by the same bolt and nut sets 4042 which hold the foot and leg joints assembled.

When the height to which the jack is desirably adiusted exceeds that which may be had by extending the screw 24 and piston IS a reasonable distance, leg extension members 52 are preferably inserted as in Fig. 2. The leg extension members 52 are formed of the same size tubing as a leg 36 itself and have sockets 54 (see Fig. '7) corresponding to the sockets in the foot members 36 into which the lower ends of the legs 30 extend. The lower ends of the leg extensions are turned in and rounded in a manner duplicative of the lower ends 36 of the legs (see Fig. 1a) The transverse holes 56 and 58 for the bolts 40 must be exactly the same distance from the lower end of the extension and the bottom of the socket as they are in the leg and foot assembly.

When the leg extensions 52 are added as in Fig. 2, the same braces 46, which formerly connected the ears 44 to the leg and foot assembly joint of Fig. 1a are used. Additional braces 60 are provided to support the joints between the lower end of the leg extensions 52 and the feet 36. Additional bolts 40 and wing nuts 42 secure the braces to the lower joints.

Where two leg extensions 52 need to be added to obtain the required height, a structure as shown in Fig. 3 is set up. Here the braces 46 and 60 remain attached to the lower head 14 as in Fig. 2 but a tubular vertical brace 62 and longer horizontal braces 64 are added, the lower end of the vertical brace 62 and the inner ends of the horizontal braces 64 both being joined to the special bracket 10, the outline of which is shown in Fig. 5. Vertical brace 62 has a flange 66 at each end, these flanges having an outside diameter substantially equal to the diameter of the central part 68 of the bracket 10 as shown in Fig. 5, which is also the diameter of the finished pad on the underside of the lower cylinder head I4. Bolts 12 extend through the flanges 66 into tapped holes in bracket 10 and into corresponding tapped holes in the bottom of the cylinder head I4.

On bracket Ill, as on the lower cylinder head l4, the three radially extending spokes 43 each carry two ears 44. Each pair of the ears 44 of bracket 10 have attached thereto a pair of braces 6464, as shown in Fig. 5. the two braces 64 of a pair, as here attached, converging to a foot joint where they are secured by a bolt 40 and wing nut 42. It should be noted here (see Fig. 8), that the spokes 43 are angularly intermediate the pairs of lugs 26 on the upper head 12, whereby the diagonally extending ears 44 form widely spaced pairs for the inner ends of the braces which provide circumferential, as well as radial, bracing for the legs.

In adding another leg extension 52 to the twice extended structure Fig. 3, the vertical brace 62 and the horizontal braces 84 are retained and a new brace is added (see Fig. 4). The new braces 80 are held to the same ears 44 with the same bolts 48 and wing nuts 50 as the braces. Fig. 3, modified as in Fig. 4, represents a structure wherein each leg has three leg extensions.

In Fig. 6, which represents the jack with four extensions per leg, the brace 64 of Fig. 3 is unchanged, but the lower end of the brace- 80 of Fig. 4 isremoved from the foot member 36 and swung downward, then augmented by the two shorter braces 82 and 84.

The top plan view Fig. 8 shows the jack as it appears when but one leg extension per leg is employed, as indicated in Fig. 2, It will be seen that the pairs of braces, spread apart as they are at their inner ends, not only fortify the structure against radial spread of the foot members 36, but provide considerable insurance against lateral deflection.

I claim as my invention:

1. The combination, in a lifting jack, of a lifting unit having a cylindrical portion with an upper and a lower head, circumferentially spaced pairs of leg hinge lugs on the upper head, leg members having their upper ends hinged, one between the ings of each pair, foot members having sockets in their upper ends to receive the lower ends of the leg members, circumferentially spaced spokes on the lower head, angularly intermediate said pairs of lugs, pairs of brace-attaching ears extending from the outer ends of said spokes, said spokes and ears extending in a plane transverse to the axis of said heads, two widely spaced ears of said brace attaching ears, one emanating from each of two adjacent spokes constitutlng a pair, pairs of braces, each pair having their inner ends secured to the spaced apart ears of a pair and their outer ends converging to opposite sides of one of said foot members, and a single means securing the outer ends of a pair of braces. a foot member, and a leg member together.

2. The combination, in a lifting jack, of a lifting unit having a cylindrical portion with an upper and a lower head, circumferentially spaced pairs of leg hinge lugs on the upper head, leg members having their -upper ends hinged, one between the lugs of each pair, leg extension members having sockets in their upper ends to receive the lower ends of the leg members, foot members having sockets in their upper ends to receive the lower ends of the leg extensions, circumferentially spaced spokes on the lower head angularly intermediate said pairs of lugs, pairs of brace-attaching ears extending from the outer ends of said spokes, said spokes and ears extending in a plane transverse to the axis of said heads, two widely spaced ears of said brace attaching ears, one emanating from each of two adjacent spokes, constituting a pair, to pairs of braces for each leg, each having their inner ends secured to the spaced apart ears of a pair and their outer ends converging to opposite sides of one of said sockets, and a single means at each socket to attach the outer ends of one pair of said braces to each of said sockets.

3. The combination, in a lifting jack, of a lifting unit having a cylindrical portion with an.

upper and a lower head, circumferentially spaced pairs of leg hinge lugs on the upper head, leg members having their upper ends hinged, one between the lugs of each pair, leg extension memends of the leg extensions, a vertical column secured to the underside of said lower head, a brace-supporting bracketat the lower end of said column, circumferentially spaced spokes on the lower head and on said bracket, the spokes on both being angularly intermediate said pairs of lugs, pairs of brace-attaching ears extending from the outer ends of said spokes, said spokes and ears extending in a plane transverse to the axis of said heads and bracket, two widely spaced ears of said brace attaching ears, one emanating from each of two adjacent spokes, constituting a pair, three pairs of braces for each leg, two of the pairs each having their inner ends secured to the spaced apart ears of a pair on the lower head and their outer ends converging to opposite sides of legextension sockets, the other of the three pairs having the inner ends secured to pairs of spaced apart ears of the bracket and their outer ends converging to opposite sides of the sockets o! the foot members, and a single means at each socket to attach the outer ends of one pair of said braces to each of said sockets.

4. The combination, in a lifting jack, of a lifting unit having a cylindrical portion with an upper and a lower head, circumferentially spaced pairs of leg hinge lugs on the upper head, leg members having their upper ends hinged, one between the lugs of each pair, leg extension members having sockets in their upper ends to receive the lower ends of the leg members or other leg extension members, i'oot members having sockets in their upper ends to receive the lower ends of the leg extensions, a vertical column secured to the underside of said lower head, a brace supporting bracket at the lower end of said column,

circumferentially spaced spokes on the lower head i and on said bracket, the spokes on both being angularly intermediate said pairs of lugs, pairs of brace-attaching ears extending from the outer ends of said spokes, said spokes and ears extendmg in a plane transverse to the axis of said heads and bracket, two widely spaced ears 01 said brace attaching ears, one emanating from each of two adjacent spokes, constituting a pair, four pairs of braces for each leg, two of the pairs each having their inner ends secured to the spaced apart ears oi a pair on the lower head and their outer ends converging to opposite sides of leg extension sockets, the other two of the four pairs having the inner ends secured to pairs of spaced apart ears of the bracket and their outer ends converging to opposite sides of the sockets; one of the two pairs to a leg extension socket and the other pair to a root member socket, and a single means at each socket to attach the outer ends of one pair of said braces to each of said sockets.

5. The combination, in a lifting jack, of a lifting unit having a cylindrical portion with an upper and a lower head, circumferentially spaced pairs of leg hinge lugs on the upper head, leg members having their upper ends hinged, one between the lugs of each pair, a plurality of leg extension members having sockets in their upper ends to receive the lower ends of the leg members, foot members having sockets in their upper ends to receive the lower ends of the leg extensions, a vertical column secured to the underside or said lower head, a brace-supporting bracket at the lower end of said column, circumferentially spaced spokes on the lower head and on said bracket, the spokes on both being angularly intermediate said pairs of lugs, pairs of braceattaching ears extending from the outer ends of said spokes, said spokes and ears extending in a plane transverse to the axis of said heads and bracket, two widely spaced ears of said brace attaching ears, one emanating from each of two adjacent spokes, constituting a pair, a plurality of pairs of braces for each leg, said pairs being divided into two groups, one group having their inner ends secured to the spaced apart career a pair on the lower head, and the other group having their inner ends secured to the spaced apart ears of a pair on the bracket, and both groups having the outer ends of each pair converging to opposite sides of one of said sockets, and a single means at each socket to attach the outer ends of one pair of said braces to each of said sockets.

THOMAS AHAWOND. 

